This invention relates to surface acoustic wave (SAW) devices. It relates, more particularly, to an economical technique for the production of SAW devices having many distinct configurations, such as coded SAW devices.
Coding and decoding apparatus has many applications, among which are position location, aircraft identification, and communications systems. Although a variety of coding and decoding apparatus has been developed, a common drawback has been the high cost of making these devices, which has limited their application in many instances to situations where technical requirements override cost considerations. However, there are a large number of applications for these coding and decoding apparatus which would benefit if a low cost way of constructing such apparatus could be developed. For example, a low cost way to manufacture coding and decoding apparatus would greatly enlarge their application to the broad field of consumer electronics, as well as to other areas.
The use of coded SAW devices as filters and correlators has been known for some time, as described in Chapter 7, pages 307-317, of a text entitled "Surface Wave Filters" edited by Herbert Matthews copyrighted 1977 by John Wiley & Sons, Inc. Although large numbers of identical SAW devices can generally be made economically in large scale production, making coding and decoding devices requires the manufacture of small numbers of dissimilar devices because of the different codings required. For example, several thousand individual codes may be required. Making small numbers of dissimilar devices prevents the low cost manufacture normally associated with the production of SAW devices.